https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111493
Bug ID: 111493
Summary: [concepts] multidimensional subscript operator inside
requires is broken
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: elrodc at gmail dot com
Target Milestone: ---
Two example programs:
> #include <concepts>
> constexpr auto foo(const auto &A, int i, int j)
> requires(requires(decltype(A) a, int ii) { a[ii, ii]; }) {
> return A[i, j];
> }
> constexpr auto foo(const auto &A, int i, int j) {
> return A + i + j;
> }
> static_assert(foo(2,3,4) == 9);
> #include <concepts>
> template <typename T, typename S>
> concept CartesianIndexable = requires(T t, int i) {
> { t[i, i] } -> std::convertible_to<S>;
> };
> static_assert(!CartesianIndexable<double,int>);
These result in errors of the form
error: invalid types 'const int[int]' for array subscript
Here is godbolt for reference: https://godbolt.org/z/WE66nY8zG
The invalid subscript should result in the `requires` failing, not an error.
